Arrangement for securing conductors in rotor slots of dynamoelectric machine

ABSTRACT

A rotor construction for a dynamoelectric machine is provided with the usual arrangement of longitudinally extending slots within which to receive the conductor bars of a distributed winding. Retainer bars making a dovetail connection with the outer ends of the rotor slots serve to secure the slot conductors in place, and end portions of these retainer bars extend beyond the rotor slots so as to overlie the end turn portions of the winding. In order to hold these portions of the retainer bars in place over the end turn portions of the winding a double layer helical wire winding is applied. The layers are wound from a single length of wire, which is of rectangular cross section and preferably made of a material which has high tensile strength and is also conductive such as bronze, and the opposite ends of the wire are anchored to the end heads of adjacent retainer bars. The wire is also soldered to the retainer bars so as to establish a short circuit ring interconnecting all of the retainer bars, also conductive, which thereby establishes a cage similar to that used in asynchronous motors.

United States Patent [72] Inventor Jacques Le Henaff Paris, France [21]Appl. No. 44,516 [22] Filed June 8, 1970 [45] Patented Jan. 11, 1972[73] Assignee Compagnie Electro-Mecanique Paris, France [32] PriorityJune 17, 1969 [33] France [31] 6920134 [54] ARRANGEMENT FOR SECURINGCONDUCTORS 1N ROTOR SLOTS OF DYNAMOELECTRIC MACHINE 1 Claim, 9 DrawingFigs.

[52] U.S.C1 310/214, 310/270, 310/271 [51] Int. Cl 1'102k 3/48 [50]Field of Search 310/214, 270, 271

[56] References Cited UNITED STATES PATENTS 3,008,786 11/1961 Costello310/214 3,065,367 11/1962 Costello et al.. 310/271 3,048,725 8/1962Wesolowski.... 310/271 1,769,816 7/1930 Yokota 310/271 PrimaryExaminer-William H, Beha, Jr. Assistant Examiner-Mark O. Budd Attorney-Pierce, Scheffler & Parker ABSTRACT: A rotor construction for adynamoelectric machine is provided with the usual arrangement oflongitudinally extending slots within which to receive the conductorbars of a distributed winding. Retainer bars making a dovetailconnection with the outer ends of the rotor slots serve to secure theslot conductors in place, and end portions of these retainer bars extendbeyond the rotor slots so as to overlie the end turn portions of thewinding. In order to hold these portions of the retainer bars in placeover the end turn portions of the winding a double layer helical wirewinding is applied. The layers are wound from a single length of wire,which is of rectangular cross section and preferably made of a materialwhich has high tensile strength and is also conductive such as bronze,and the opposite ends of the wire are anchored to the end heads ofadjacent retainer bars. The wire is also soldered to the retainer barsso as to establish a short circuit ring interconnecting all of theretainer bars, also conductive, which thereby establishes a cage similarto that used in asynchronous motors.

PATENTED JAN! 1 I972 SHEET 2 0F 2 -4 III Jacques Le HenaFf wwx 1ARRANGEMENT FOR SECURING CONDUCTORS IN ROTOR SLOTS OF DYNAMOELECTRICMACHINE This invention relates to dynamo-electric machines and isdirected to an improvement in the construction of the rotor elements ofsuch machines. More particularly, the invention is concerned with thegeneral problem of securing the rotor winding in place so as to preventdislodgm'ent due to the strong centrifugal forces which are set up onthe rotor conductors as the rotor turns at relatively high speeds.

It is conventional, in the construction of rotors of dynamoelectricmachines, to locate the conductors of the winding in longitudinallyextending slots opening to the surface of the rotor, and to retain theconductors in the slots by means of bars which close the mouths of theslots, the bars being retained in place by means of a dovetailconnection with the walls of the rotor slots.

These retainer bars project beyond the ends of the longitudinallyextending rotor slots and cover the head portions of the rotorconductors, i.e. those portions of the winding which extend partiallyaround the rotor in the peripheral direction in leaving one slot andreentering another slot. These end portions of the bars cannot, ofcourse, be dovetailed into the body of the rotor where they overlie thehead portions of the winding and hence, are subject to centrifugalstresses which tend to throw them in a radially outward direction.Similar centrifugal forces exerted on the head ends of the rotor windingalso add to the difficulty since these head portions likewise tend to bethrown radially outward against the bars. Thus, to prevent dislodgementof the head ends of the winding and also of the overlying end portionsof the slot conductor retainer bars, it is necessary to utilize specialretainer means.

One well-known retainer structure is constituted by a massive sleevewhich surrounds the end portions of the retainer bars, the sleeve beingheated and then shrunk into place over the bars. However, because of theintense radial forces exerted on the head or end turn portions of therotor winding and the end portions of the retainer bars, the sleeve isrequired to have substantial thickness. In certain applications,however, it is not possible to tolerate a retainer sleeve of substantialthickness, one reason being that the allowable thickness of the sleevemust be less than a maximal value imposed by dimensional characteristicsof the machine. Another reason is that the retainer sleeve functionsalso as a short-circuit ring which can, therefore, give rise tosubstantial heating to the currents induced thereon.

The object of the present invention is therefore to provide an improvedretainer construction for the slot conductor retainer bars, i.e. forthose end portions of the bars which overhang the head portions of therotor winding, which is not only mechanically strong but also has theadvantage of being relatively thin.

More particularly, in accordance with the invention, the retainerstructure is constituted by a multiple layer type winding of coaxialhelices wound from a single length of wire and which surround theretainer bars, the opposite ends of the wire being anchored on headportions at the ends of adjacent retainer bars.

The wires from which the two helices are wound is preferably alsoelectrically conductive, so that it together with the peripheral arrayof retainer bars on which it is wound establishes a short circuited cageof the type utilized with "asychronous motors.

The wire chosen for the retainer, must also have a very high mechanical,i.e. tensile strength and is thus made from a material having suchcharacteristic, such as, for example, bronze.

The wire type retainer structure in accordance with the invention offersthe advantage of providing maximal security for the end portions of theslot conductor retainer bars which extend beyond the longitudinal slotsin the rotor, when the rotor is turning at high speeds.

One suitable embodiment of the invention is described hereinafter indetail and is illustrated in the accompanying drawings wherein:

FIG. 1 is a partial longitudinal view of a rotor from one end thereoftowards the middle, the lower half being shown in elevation and theupper half in section;

FIG. 2 is a partially developed view of the rotor of FIG. 1, drawn to alarger scale;

FIG. 3 is an end view of a portion of the rotor;

FIG. 4 is a view partially in plan and partially in section of an endportion of a bar used to retain the head portion of the conductors ofthe rotor winding.

FIG. 5 is a transverse sectional view taken on line VV of FIG. 4;

FIG. 6 is a plan view, drawn to larger scale than FIG. 4, of a similarend portion of another retainer bar;

FIG. 7 is a transverse sectional view taken on line Vll-Vll of FIG. 6;

FIG. 8 is also a plan view, also drawn to a larger scale than FIG. 4 ofa similar end portion of another retainer bar; and

FIG. 9 is a transverse sectional view taken on line IX-IX of FIG. 8.

With reference now to the drawings, and to FIG. [-3 in particular, therotor of the dynamoelectric machine is constituted by the usualelongated cylindrically shaped iron body 1 provided on its peripherywith longitudinally extending slots 2 in which are lodged the conductors3 of the rotor winding, there being usually several conductors seated ineach rotor slot. In order to hold the conductors 3 in their slotsagainst the centrifugal force which arises as the rotor is rotated athigh speed, it will be seen that the entrance to each slot is given atrapezoidal configuration which thereby forms a dovetail in which isreceived a complementary trapezoidal configured portion 4b of a metallicand preferably electrically conductive retainer bar 4, the bar 4 beingalso provided with another portion 4a having an elongated rectangularcross section which overlaps the side edges of the rotor slot at itsentrance.

The end portions of the retainer bars 4 extend beyond the longitudinallyextending conductor slots in the rotor and lie above the head i.e. endturn portions 5 of the winding which extend in the circumferentialdirection in circumferential slots, after they leave the longitudinalrotor slots, for a certain distance so that they can reenter otherlongitudinal slots in the rotor. The end portions of the retainer bars4, which extend beyond the longitudinal rotor slots and overlie the headportions 5 of the windings, unlike the remaining portions of bars 4which are secured by their dovetailed interengagement with thelongitudinal rotor slots, have nothing to secure them against theradially outward forces which arise as a result of rotor rotation. Inaccordance with the present invention, these end portions of theretainer bars 4 function to hold the head portions of the rotor windingsecurely in place, and are themselves held securely in place by a novelretainer structure constituted by a multiple layer, helical wirewinding, the wire preferably being made of an electrically conductivematerial and which also has a high degree of tensile strength such as,for example, bronze. Being electrically conductive and in contact withthe array of retainer bars which surround the rotor in parallel spacedrelation and are also electrically conductive, the bars and wireretainer together establish a cage of shortcircuited conductors similarto that utilized in asynchronous motor construction.

The wire type retainer structure 6 for the end portions of the bars 4 isformed from a wire 7, preferably of rectangular cross section. Wire 7 iswound around the peripheral array of the bars 4 in a thinned out portionof the latter established by removing the outer rectangular portion 4a,thus leaving only the trapezoidal configuration portion 412. The wire 7is also wound in two superposed coaxial helical layers 6a and 612 fromone length of wire and the ends of the wire are suitably anchored inespecially configured heads formed on the extreme outer ends of fouradjacent bars 4.

With reference now to FIGS. 2 and 3, it will be seen that the end heads8, 9, l0 and l l of four adjacent bars 4 have a transverse configurationwhich is essentially the same as that of an intermediate portion of thebar associated with a longitudinal slot in the rotor. That is, each ofthese end heads 8 to 11 ineludes an outer portion 4a of elongatedrectangular cross section and an inner portion 4b of trapezoidal crosssection which is entered into and retained by a longitudinal groove inthe rotor of complementary configuration so as to establish a dovetailtype of interconnection.

The heads 8' to 11 are especially machined so as to provide anchorpoints for the opposite ends of the wire 7, and to enable the wire endsto be additionally secured at those anchors by means of plates 12 to 14which are wedged into place against the wire ends between overhangingportions of the rectangular parts 4a and the surface of the rotor.

The anchoring end heads 9 and of the two centrally located bars 4 of thegroup of four adjacent bars are machined in the same manner, accordingto the configuration depicted in detail in FIGS. 4 and 5. As can be seenin these two views, two longitudinally grooves 9a, 9b are formed inopposite sidewalls of the head 9, these grooves being slightly inclinedwith respect to the longitudinal axis of the bars and converging to theexterior of the rotor. The anchoring end head 10 is machined in the samemanner as head 9 and is also provided with two opposite grooves 10a and10b.

As distinguished from the heads 9 and 10, the two outer heads 8 and l 1of the outermost bars of the four bar group are machined so as to haveonly one groove 8a (11a) these grooves being symmetrical with respect toa radial plane as is evident from an inspection of FIGS. 6 to 9.

Anchoring of the two ends of wire 7 is accomplished in the mannerdepicted quite clearly in FIG. 2. First, one end 7a of the wire isengaged in groove 10b of anchoring head 10 of a bar 4 and it is thenbent back into a U-shape so that a subsequent part 711 of the wire islodged in the other groove 10a. With this end of the wire anchored, thewire is then wound in helical form around and on the trapezoidalsectioned parts 4b of the peripheral array of bars 4 to form the firstlayer 6b, the winding proceeding in the direction away from the heads8-11. After the first helical layer 6b has been wound, the secondhelical layer 60 is wound proceeding in the opposite direction andarriving back at the heads 8 11. A portion 7c near the end of the wireis then engaged in groove 9a of head 9 facing groove 10a of head 10, thewire is bent back into U- shape, and finally the extreme end 7d of thewire is engaged in groove 9b of anchor head 9.

To ensure that the ends 711 to 7d of the wire 7 will be retained inplace in the grooves provided in the heads, the plates 12, 13 and 14 arethen force-fitted longitudinally into place between the head 4a and therotor surface. As shown in FIG. 2, one side of plate 12 engages groove8a of head 8 and the other side engages the wire end 7d. The centrallylocated plate 13 which is longer than plates 12 and 14, has its oppositesides tightly engaged with the wire portions 7b and 7c, and the plate 14has one side engaged with the wire end 7a and the other side with groove11a of head 1 1.

After the plates l2, l3 and 14 are fitted into place against the endportions of wire 7, one may then solder the plates to the wire 7 andalso to the clamping heads 8 to 11 if additional security againstdislodgment of the plates and wire is desired.

When finished, the wire retainer 6 is thus seen to consist of a radiallyinner helical winding 6a applied to the end portions of the bars 4, anda radially outer helical winding 6b applied directly upon the innerwinding 6b, the two winding layers being of the same axial length, andwith the adjacent convolutions of each helix in contact with each other,as depicted in FIG. 1. Moreover, since the wire has a rectangular crosssection and adjacent convolutions are in contact with each other, eachhelical layer has essentially the same amount of material as a solidsleeve of the same dimensions.

The helical wire retainer 6, in addition to functioning as a means forbinding the end portions of the bars 4 and head portions of the rotorwinding in place, also has the additional advantage, due to the wire 7being also electrically conductive, of functioning to establish a shortcircuit for all of the bars 4, also conductive, on the rotor, thusforming a cage of the type which is associated with asychronous typemotors. In order to improve the electrical connection and ence the shortcircuit,

the wire 7 can be soldered to the bars 4.

A further advantage of the helical wire retainer 6 is that as a resultof the unique anchoring device, it has a very smooth external surfacethus permitting only very small mechanical gaps.

In conclusion, it is desired to note that the illustrated embodiment ofthe invention is to be considered as typical only, and that one maydepart in detail from the particulars of the illustrated constructionwithout, however, departing from the spirit and scope of the inventionas defined in the appended claims. a

I claim:

1. In a rotor construction for a dynamoelectric machine the combinationcomprising a cylindrical rotor provided with a peripheral array oflongitudinally extending slots in the outer surface thereof, adistributed winding for said rotor including conductor bars havinglongitudinally extending conductor portions disposed in said slots andend turn portions extending beyond said slots and which extend in acircumferential direction, retainer bars located in said rotor slotsabove the conductor bars for retaining the conductor bars in the slots,and retainer bars extending longitudinally to provide end portions whichoverlie said end turns on said winding and which terminate in end headseach including a trapezoidal configured portion engaged in acomplementary configured slot in the rotor and a rectangular configuredportion disposed above the surface of the rotor, a double layer helicalwire winding applied on said end portions of said retainer bars forretaining said end turn portions of said conductor bars in place, saiddouble layer helical winding being wound from one continuous length ofwire having a rectangular cross section, the terminal ends of said wirebeing received in corresponding grooves in the end heads of adjacent endportions of said retainer bars, and plate members slidable into placebetween the undersurface of said rectangular configured portions of saidend heads and the rotor surface to engage said terminal ends of saidwire and secure them in place within said grooves.

N O T E T C. c W E m 3 ML U N O m C h F M 0 MM E T S A C I m w w v R WMPu w! w MW January 11,, 197 Dazed Patent; No. 6315709 Henaff theabove-idencifiad .pazep:

own "Dela It; is certified that error appears in and aha: said LettersPatent are, hereby cor rected as s H and" should be Claim 1, 11nd 10.-

- said I tilfis 30th dayio f May I972,

' Signed'angfaled (SEAL) Att-est ROBERT GO'ITSCHALK EDWARD MQFLETHERA'ttesting Offi-qe'r Commissioner of.Patents January 11, 1972 w; m T C FE J\ ML m N O .L HIM a Cu E r TL M m .S A C m. T m H T v- R E C 0 a TU MDated .Tgnqlms Le Hana "Lad vpanel;

W l Mb hum n e 0 dun us a s Y W& 2 t m t2 5 w u e w a e w w Ph Ir. iscertified than error a. that said Letters latem are and H and" shnuld beClaim 1,, l in l0 said Signed 'angi" s s aled 30th daypf May 1972.,

(SEAL) Attes ROBERT GOTTSGHALK Comissiongr of.Patents A'ttestingOff'iqe'r

1. In a rotor construction for a dynamoelectric machine the combinationcomprising a cylindrical rotor provided with a peripheral array oflongitudinally extending slots in the outer surface thereof, adistributed winding for said rotor including conductor bars havinglongitudinally extending conductor portions disposed in said slots andend turn portions extending beyond said slots and which extend in acircumferential direction, retainer bars located in said rotor slotsabove the conductor bars for retaining the conductor bars in the slots,and retainer bars extendinG longitudinally to provide end portions whichoverlie said end turns on said winding and which terminate in end headseach including a trapezoidal configured portion engaged in acomplementary configured slot in the rotor and a rectangular configuredportion disposed above the surface of the rotor, a double layer helicalwire winding applied on said end portions of said retainer bars forretaining said end turn portions of said conductor bars in place, saiddouble layer helical winding being wound from one continuous length ofwire having a rectangular cross section, the terminal ends of said wirebeing received in corresponding grooves in the end heads of adjacent endportions of said retainer bars, and plate members slidable into placebetween the undersurface of said rectangular configured portions of saidend heads and the rotor surface to engage said terminal ends of saidwire and secure them in place within said grooves.